Patent GB-848839-A (GB)
Title: Improvements in or relating to gas-turbine plants
IPC: F02C9/16
Filed: 1957-05-10
Abstract: 848,839. Gas turbine plant. MASCHINENFABRIK AUGSBERG-NURNBERG A.G. May 10, 1957 [Nov. 24, 1956], No. 14941/57. Class 110 (3). [Also in Group XXIX] A gas turbine plant burning a gaseous fuel in which at least one additional fuel is burnt in the event of a gaseous fuel deficiency comprising a main gas turbine, a fuel gas compressor and a combustion chamber has some of the fuel gas delivered by the fuel gas compressor heated and then expanded in an auxiliary prime mover supplying power to a gas turbine shaft before it is returned to the fuel gas compressor inlet. Air compressed in a compressor 11 is heated in a heat-exchanger 12 and supplied to a combustion chamber 13 feeding a turbine 17 driving the compressor 11. The exhaust from the turbine 17 enters a turbine 19 driving a generator 18. The exhaust from the turbine 19 is divided, part flows through the pipeline 21 to the heatexchanger 12 and part flows through an auxiliary combustion chamber 23 to a heatexchanger 16 where fuel gas supplied by a compressor 15 is heated. After passing through the heat-exchanger 16 part of the heated fuel gas is fed to the combustion chamber 13 and the remainder is passed through a pipeline 26 and control valve 27 to an auxiliary turbine 28 coupled through gearing 33 to the compressors 11, 15. The coupling 32 may be a permanent coupling or a slip coupling. The exhaust of the turbine 28 is returned through a cooler 30 to the fuel gas supply pipe 14. The fuel gas compressor 15 is designed so that at full load it supplies the requirements of fuel gas for the combustion chamber 13 and the no-load power of the auxiliary turbine 28. Liquid fuel from a tank 34 is supplied to the combustion chambers 13, 23, through control valves 38, 41. The valves 27, 38 are controlled by throttle valves 54, 62. As shown, the throttle valves 54, 62, the control-valve 27, as well as the fuel valves 38, 41 are shown in the normal position for rated power with fuel gas operation only. The control valve 27 is partially open so as to pass a quantity of fuel gas for the no-load requirements of the turbine 28. The throttle valve 62 is fully open and abuts the stop 63. As a consequence there is no pressure in the controlline 49 and fuel valve 38 is closed. Fuel valve 41 is also closed. If the load now drops, the speed governor 59 will cause rod 60 to pivot about point 60a to open throttle valve 54. Control valve 27 then opens so that the combustion chamber 13 is by-passed by the fuel gas and the speed of the turbines 17 and 19 falls. With an increase in load more fuel gas is caused to flow into the combustion chamber 13. If the quantity of fuel gas available is insufficient the pressure in the pipe 14 falls which causes the pressure regulator 57 to lift the slide 61 until the valve rod of the valve 54 abuts against a stop. The point 60b then becomes a fixed pivot so that the throttle valve 62 is closed by the governor 59. This causes the fuel valve 38 to be opened by the servomotor 48, to supply liquid fuel to the combustion chamber 13. If, with constant load, the pressure in the pipe 14 falls, the pressure regulator will open the valve 54 and close the valve 62 since the point 60c is fixed. This results in the control-valve 27 being opened to pass more fuel gas to the turbine 28 and the valve 38 being opened to allow liquid fuel to be supplied to the combustion chamber 13. If the temperature of the gases leaving the combustion chamber 13 rise above a predetermined value, the servomotor 50 is operated by the temperature-responsive device 64 to open the fuel valve 41 of the combustion chamber 23. The resulting increased power of the turbine 28 causes more air to be delivered to the combustion chamber 13 so that the temperature is reduced. The control valve 27 may be replaced by a number of control valves, each associated with an individual nozzle segment, which are opened or closed successively. An independent nozzle segment of the turbine 28 may be supplied with compressed air or steam and used as a starting motor for the gas turbine plant. The turbines 17, 19 may be on one shaft. The fuel gas compressor 15 is preferably of the radial flow or centrifugal type.